Backgrounds and Objectives: Mercury is a heavy metal that is widespread in the environment and has many toxic effects. At present, MeHg exposure on women remain an important issues for researching, especially those of continuous uptake in high-fish consumption.MeHg can be transferred to infant through breast milk. The objective of this study was to characterize the risk of Hg exposure in mothers in south of the Caspian Sea.Materials and Methods: In this study mercury in hair of 70 breast-feeding women (17-36 years old) and influencing factor on it, were assessed. Mothers lives in nur, nowshahr and chamestan cities and villages of Nur and Nowshahr. In order to researching on influencing factors, mothers fill questionnaires. Hair samples (about 1 gr) were obtained from mothers. The mercury was measured by LECOAMA254AdvancedMercuryAnalyzer (USA) according toASTM, standard NO.D-6722.Results: Total mean mercury concentration in mothers hair obtained 0.19±0.09 ( &mug gr-1). Tukey test show that the influence of the variables place of live (p=0.02), fish and sea food consumption of mother (P=0.00) were significantly affected on hair mercury concentration of mothers. The other factors (age and number of dental amalgam filling ) had no significant effect on mercury levels in hair of mothers.Conclusion: Total mean mercury concentration in mothers hair were lesser than normal dose recommended byWHO (2&mug g-1) and EPA reference (5 &mug g-1). Analysis of questionnaires showed that three kinds of fish including carp, golden mulle and kutum. Although were often used in this study, mercury concentration in fish was not determined, but in according to significate relation between fish consumption and mercury concentration in mother#s hair, pollution with mercury in the fish can be the main factor of mercury exposure in this study.